Heatsink mounting system with overhang damping

ABSTRACT

In one embodiment, a heatsink mounting system includes a plurality of fasteners for attaching the heatsink to a circuit board at a location proximate to an electronic component interposed between the circuit board and the heatsink and a damping connector for attaching an overhang portion of the heatsink to the circuit board. The damping connector includes a first O-ring for positioning adjacent to an upper surface of a base of the heatsink, a second O-ring for positioning adjacent to a lower surface of the base, and a connecting member extending through aligned openings in the O-rings and the base of the heatsink. The damping connector is operable to absorb energy during vibration or shock at the heatsink to prevent flexing of the heatsink.

TECHNICAL FIELD

The present disclosure relates generally to heatsinks, and moreparticularly, to heatsink damping.

BACKGROUND

Over the past several years, there has been a tremendous increase in theneed for higher performance communications networks. Increasedperformance requirements have led to an increase in energy use resultingin greater heat dissipation from components. Heatsinks are widely usedto accommodate the large thermal dissipation of many semiconductordevices. High power components such as ASICs (Application SpecificIntegrated Circuits) require larger high performance heatsinks, whichare sensitive to bowing under shock and vibration conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective illustrating an example of a heatsink mounted ona circuit board.

FIG. 2 is a partial top view of the circuit board of FIG. 1 with theheatsink removed.

FIG. 3 is a perspective of the heatsink and a heatsink mounting system,in accordance with one embodiment.

FIG. 4 is an enlarged partial view of the heatsink and mounting systemshown in FIG. 3.

FIG. 5 is a side view of the heatsink mounted on the circuit board withthe mounting system.

FIG. 6 is a schematic illustrating forces on the heatsink and a dampingconnector during shock or vibration, in accordance with one embodiment.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

In one embodiment, a heatsink mounting system generally comprises aplurality of fasteners for attaching the heatsink to a circuit board ata location proximate to an electronic component interposed between thecircuit board and the heatsink and a damping connector for attaching anoverhang portion of the heatsink to the circuit board. The dampingconnector comprises a first O-ring for positioning adjacent to an uppersurface of a base of the heatsink, a second O-ring for positioningadjacent to a lower surface of the base of the heatsink, and aconnecting member for extending through aligned openings in the O-ringsand the base of the heatsink. The damping connector is operable toabsorb energy during vibration or shock at the heatsink to preventflexing of the heatsink along a length of the heatsink.

In one or more embodiments, the connecting member comprises two matingconnectors each comprising a shoulder for supporting the O-ring.

In one or more embodiments, the O-rings are installed in an uncompressedstate to provide zero static load on the heatsink.

In one or more embodiments, the fasteners comprise four spring loadedscrews and the damping connector comprises two damping connectorspositioned along an edge of the overhang portion of the heatsink.

In one or more embodiments, the heatsink base comprises a two-phasedevice to remove heat generated by the electronic component. Thetwo-phase device may comprise a vapor chamber.

In one or more embodiments, the heatsink comprises a plurality of finsextending from the base and the damping connector comprises two dampingconnectors positioned at corners of the overhang portion of the heatsinkand aligned with a recessed portion of the fins.

In one or more embodiments, the heatsink has an aspect ratio of width tolength of at least one to three.

In another embodiment, an apparatus comprises a heatsink, a plurality offasteners for attaching the heatsink to the circuit board at a locationproximate to an electronic component interposed between the circuitboard and the heatsink, and a damping connector for attaching anoverhang portion of the heatsink to the circuit board. The dampingconnector comprises a first O-ring adjacent to an upper surface of abase of the heatsink, a second O-ring adjacent to a lower surface of thebase of the heatsink, and a connecting member extending through alignedopenings in the O-rings and base of the heatsink. The damping connectoris operable to absorb energy during vibration or shock at the heatsinkto prevent flexing of the heatsink along a length of the heatsink.

In yet another embodiment, an apparatus comprises a circuit board, aheatsink mounted on the circuit board, a plurality of fastenersattaching the heatsink to the circuit board at a location proximate toan electronic component interposed between the circuit board and theheatsink, and a damping connector attaching an overhang portion of theheatsink to the circuit board. The damping connector comprising a firstO-ring adjacent to an upper surface of a base of the heatsink, a secondO-ring adjacent to a lower surface of the base of the heatsink, and aconnecting member extending through aligned openings in the O-rings andbase of the heatsink and attached to the circuit board. The dampingconnector is operable to absorb energy during vibration or shock at theheatsink to prevent flexing of the heatsink along a length of theheatsink.

Further understanding of the features and advantages of the embodimentsdescribed herein may be realized by reference to the remaining portionsof the specification and the attached drawings.

Example Embodiments

The following description is presented to enable one of ordinary skillin the art to make and use the embodiments. Descriptions of specificembodiments and applications are provided only as examples, and variousmodifications will be readily apparent to those skilled in the art. Thegeneral principles described herein may be applied to other applicationswithout departing from the scope of the embodiments. Thus, theembodiments are not to be limited to those shown, but are to be accordedthe widest scope consistent with the principles and features describedherein. For purpose of clarity, details relating to technical materialthat is known in the technical fields related to the embodiments havenot been described in detail.

High power components such as ASICs (Application Specific IntegratedCircuits) often need larger high performance heatsinks, which mayinclude two-phase cooling components such as vapor chambers or heatpipes to quickly dissipate and spread excessive heat to fins, which arecooled via forced airflow. Lower performance heatsinks are typicallysmaller and shaped so that the heatsink can be symmetrically positionedover an electronic component. As such, a downward force created due tocoupling of the heatsink to a circuit board is evenly distributed overthe electronic component, which prevents the heatsink from undergoingstructural deformation and allows for optimal heat transfer. Due togrowing power requirements and corresponding cooling requirements forelectronic components, heatsinks are increasing in size and complexityso that when the heatsink is coupled to the circuit board, the heatsinkis no longer symmetrical relative to the underlying electroniccomponent. Limited board space and electrical component constraintsoften results in an asymmetrical layout of the heatsink, which increasesattachment challenges due to a cantilever effect. A challenge withlarger high performance heatsinks is therefore not just the heattransfer but also the mechanical integrity of the heatsink due to thesize, weight, and shape. For example, the sensitivity of vapor chamberheatsinks or other high performance heatsinks is highly correlated tothe overall flatness of the heatsink. When the heatsink aspect ratio islarge (e.g., 1 to 3 ratio of width to length or other ratio), theheatsink may be subject to bowing (flexing along the length of theheatsink). The vapor chamber heatsink may be particularly prone tobowing due to the weight and thin structure of its base. The bowing maylead to damage of fluid cooling components (e.g., vapor chamber, heatpipes) in the heatsink and BGA (Ball Grid Array) cracking on the circuitboard and electrical component connections, for example.

In order to prevent bowing, asymmetrical heatsinks may be attached tothe circuit board using additional mounting points to distribute loadingacross a larger area. However, this takes up valuable printed circuitboard space. Also, the asymmetrical layout relative to the underlyingelectrical component prevents the even distribution of downward forcewith conventional mountings. A portion of the heatsink extending beyondthe electronic component (referred to herein as an overhang portion)needs to be secured to the circuit board in order to meet shock andvibration requirements, maintain optimum flatness of the heatsink base,and ensure heatsink thermal performance, while having minimal impact oncircuit board layout due to mounting holes.

The embodiments described herein comprise a heatsink mounting system forattaching a heatsink to a circuit board and providing damping support toan overhang portion of the heatsink that does not directly cover anelectronic component over which the heatsink is positioned. In one ormore embodiments, damping is provided through a pair of O-rings(compressible members/elements) located on a top and bottom side of aheatsink base to absorb a cantilever force during shock and vibration.

Referring now to the drawings, and first to FIG. 1, an example of aheatsink 10 mounted on a circuit board (e.g., printed circuit board) 12is shown. The heatsink 10 transfers heat generated by an electroniccomponent such as a semiconductor device (e.g., ASIC) where heatdissipation capability of the component is insufficient to moderate itstemperature. As described in detail below, the heatsink 10 includes abase and fins, which allow excess thermal energy to dissipate into theenvironment by conduction and convection. The heatsink 10 is configuredto maximize the surface area in contact with a cooling medium (e.g.,air) surrounding the heatsink. The heatsink 10 may be formed from anysuitable material (e.g., copper, aluminum, or other material) havingrelatively high heat conduction characteristics to allow heat transferfrom the electronic component to the heatsink and have any shape (e.g.,height, width, length, ratio of width to length, base footprint, basethickness, number of fins, size of fins). In one or more embodiments,the heatsink 10 comprises a two-phase device (e.g., vapor chamber, heatpipes) to improve thermal performance. The vapor chamber or heat pipesmay be located in the base of the heatsink, for example. The two-phasedevice transfers heat through the phase change of liquid to vapor andback to liquid, with the liquid passively pumped from condenser toevaporator by capillary action.

As shown in the example of FIG. 1, the circuit board (e.g., printedcircuit board) 12 may comprise any number of optical modules 14,asymmetric heatsink 10, symmetric heatsink 16, electronic components,interfaces, or other components (e.g., fan, power supply). The printedcircuit board 12 provides a dielectric material for copper or otherconductive traces. The traces and pads are embedded within or depositedon the printed circuit board 12 for connection with the electroniccomponents. Etching, deposition, bonding, or other processes may be usedto form the traces, pads, or embedded components (e.g., passive oractive devices). The printed circuit board 12 may include one or moreactive devices (e.g., transistor, chip, processor, circuit, applicationspecific integrated circuit, field programmable gate array, memory,etc.) and one or more passive devices (e.g., capacitor, resistor,inductor, connector, via, pad, etc.). Vias may be provided for routingtraces through layers of the printed circuit board. The traces, pads,and electronic components may be arranged in any configuration toperform any number of functions (e.g., network server card, graphicscard, motherboard, device card (line card, fabric card, controllercard), and the like) for operation on any type of network device (e.g.,computer, router, switch, server, gateway, controller, edge device,access device, aggregation device, core node, intermediate node, orother network device). The circuit board 12 may be contained within aframe 15 and located within a line card, fabric card, controller card,or other modular device, including, for example, 1RU (rack unit), 2RU,or other size modular devices. The network device may operate in thecontext of a data communications network including multiple networkdevices that communicate over one or more networks.

As described below with respect to FIG. 2, the heatsink 10 isasymmetrically positioned over an electronic component (e.g., ASIC) dueto its size in order to support cooling capacity provided by a highperformance heatsink. Damping connectors 18 support an overhang portionof the heatsink 10 and provide damping to reduce amplitude or vibrationquickly and effectively. The mounting system further includes fasteners(e.g., spring loaded screws) 19 used to mount a symmetric portion of theheatsink to provide contact between the electronic component and theheatsink 10.

FIG. 2 is a partial top view of the circuit board 12 of FIG. 1 showingan electronic component (e.g., ASIC) 20 positioned below the heatsink 10(FIG. 1), with the heatsink removed to show mounting details relative tothe ASIC. An outline of the removed heatsink is indicated at 25 in FIG.2. As illustrated in FIG. 2, the heatsink has an asymmetrical layoutrelative to the underlying ASIC 20. Mounting holes 22 are used to mounta symmetric portion of the heatsink 10 to the circuit board at alocation proximate to the electronic component 20 interposed between theheatsink and the circuit board 12. As noted above with respect to FIG.1, spring loaded screws 19 (or other suitable fasteners) may be used tomount the heatsink to the circuit board 12 at mounting holes 22. Thefasteners 19 used to couple the heatsink 10 to the circuit board 12 atmounting locations 22 (FIGS. 1 and 2) create a downward coupling force(where the downward direction is defined as a direction from theheatsink 10 to the circuit board 12). For optimal heat transfer, thelocation and spring force on the fasteners 19 are calculated such thatuniform force spreads evenly across the ASIC 20.

In order to counter the asymmetrical downward coupling force created dueto the asymmetrical layout of the heatsink over the ASIC 20, one or moredamping connectors are provided to counter the downward force. In theexample shown in FIGS. 1 and 2, two damping connectors 18 are installedat mounting locations 24. In this example, the damping connectors 18 arepositioned along an edge of the overhang portion of the heatsink. Thedamping connectors 18 may also be located closer to the ASIC 20,however, the connectors should not be positioned too far from the edgeto prevent another overhang portion that is free to flex under vibrationand shock.

It is to be understood that the heatsink 10 and circuit board 12described above and shown in FIGS. 1 and 2 are only examples and thatthe heatsink mounting system described herein may be used to attach anytype of heatsink to any substrate supporting electronic components. Thecircuit board may be any type of conductive platform or board forinstalling and electrically connecting electrical and mechanicalcomponents to create an electrical circuit. The circuit board may besecurely positioned within a housing and have one or more electronicchips (e.g., ASIC or other electronic component, microchip, orintegrated circuit) installed thereon. One or more heatsinks may beattached to the circuit board and positioned over one or more heatgenerating electronic components. The heatsink mounting system describedherein may be used to mount one or more heatsinks to the circuit board.

Also, it should be noted that the terms, downward, upward, bottom, top,lower, upper, below, above, and the like as used herein are relativeterms dependent upon orientation of the printed circuit board andnetwork device and should not be interpreted in a limiting manner. Theseterms describe points of reference and do not limit the embodiments toany particular orientation or configuration.

FIG. 3 is a perspective of the heatsink 10 and mounting system, inaccordance with one embodiment. The heatsink 10 includes a base plate(base) 30 and a plurality of fins 32 extending upward from the baseplate. The base plate 30 couples the electronic component to theheatsink 10 and airflow (e.g., provided by one or more fans) flowsacross the fins 32. The base plate 30 transfers the heat to the fins 32and the airflow carries heat away from the heatsink as it travels pastthe fins, thereby cooling the electronic component. As previously noted,the heatsink 10 may include a two-phase cooling device such as a vaporchamber or heat pipes to further improve thermal efficiency of theheatsink.

The heatsink 10 includes a symmetrical portion 34 mounted above andproximate to the electronic component 20 and an overhang portion 35 thatis asymmetrical relative to the underlying electronic component (FIGS. 2and 3). The base 30 comprises a plurality of openings 33 correspondingto attachment points on the circuit board 12 (e.g., 22 and 24 in FIG.2). At the location of each of the openings 33, a portion of a body ofthe heatsink (comprising fins 32) is recessed to create an opening 31for ease of access of the connector 18 or fastener 19 (insertion,removal of coupling components). These hollow (recessed) portions 31 inthe heatsink body are shown as vertical rectangular cubes above each ofthe openings 33, however, different shapes may be used to form thecutout portions in the heatsink body.

Coupling components (fasteners) 19 for mounting the symmetric portion 34of the heatsink 10 may include, for example, a spring loaded screw,spring loaded plunger, clip, and the like. In the example shown in FIG.3, four spring loaded screws 50 attach the symmetric portion 34 of theheatsink to the circuit board 12 over the ASIC 20 at mounting locations22 (FIGS. 2 and 3).

The damping connectors (connector assemblies) 18 attach the overhangportion 35 of the heatsink 10 to the circuit board at mounting points 24(FIGS. 2 and 3). Each damping connector 18 comprises a first O-ring 37for positioning adjacent to an upper surface 47 of the base 30 of theheatsink 10, a second O-ring 38 for positioning adjacent to a lowersurface 48 of the base of the heatsink, and a connecting memberextending through aligned openings in the first O-ring 37, second O-ring38, and the base 30 of the heatsink for attachment to the circuit board.In the example shown in FIG. 3, the connecting member comprises a firstscrew 36 for mating with a second screw 39. As described below withrespect to FIG. 4, the O-rings 37, 38 are supported by shoulders on thetwo mating screws 36, 39 and help to quickly reduce the amplitude ofshock and vibration at the heatsink 10. The damping connectors 18 allowthe spring loaded fasteners 19 to provide heatsink to ASIC contact whilethe end cantilever effect is addressed by the damping connectors. Thedamping connectors 18 absorb the cantilever force (dynamic energy)created during vibration or shock at the heatsink 10, as described belowwith respect to FIG. 6.

The O-rings 37, 38 may comprise, for example, rubber O-rings (e.g., EPDM(ethylene propylene diene monomer), EPR (ethylene propylene rubber),Neoprene, or any other suitable material) configured to withstandthermal conditions in the heatsink environment and provide sufficientdamping. It is to be understood that the term O-ring as used hereinrefers to any compressible element having a central opening and anycross-sectional shape (e.g., circular, oval, rectangular). The two-piecedamping design allows for optimization of damping with a wide range ofO-ring selection (e.g., material, durometer, size, shape) along withnumber and location of damping connectors.

In one example, the heatsink base 30 has a width of 3.4 inches, lengthof 11.5 inches (aspect ratio of approximately 1:3), a thickness of 1inch, and a weight of 1.8 pounds. It is to be understood that this isonly an example and the heatsink may have other shapes, sizes, weights,or aspect ratios. Also, as previously noted, the number and arrangementof connectors 18 and fasteners 19 and connectors shown in FIG. 3 is onlyan example and a different number of connectors or fasteners, ordifferent mounting locations may be used without departing from thescope of the embodiments.

FIG. 4 is an enlarged partial perspective of the heat sink 10 anddamping connectors 18 shown in FIG. 3. As shown in the exploded view ofthe damping connector 18, the screw 36 comprises a shaft 42 defining alongitudinal axis 41 and a flange/shoulder (head) 40 extendingsubstantially perpendicular to the axis 41 of the connector 18. Each ofthe O-rings (compressible members) 37, 38 defines an aperture (opening)for receiving the shaft 42 of the connecting member and encircles theshaft. The flange 40 provides a mating shoulder for the O-ring 37 on itsunderside. A tip 43 of the screw 36 is received in an opening 44 formedin a top surface of a head 46 of the mating screw 39, which provides ashoulder for the lower O-ring 38. The screw 39 comprises a shaft 45 forattachment to the circuit board 12, as shown in FIG. 5.

FIG. 5 is a side view of the heatsink 10 attached to the circuit board12 with the ASIC 20 interposed therebetween. As previously described,the symmetric portion 34 of the heatsink 10 is attached to the circuitboard 12 with fasteners 19 comprising the screw 50 inserted into aspring 52. A shaft 55 of the screw extends through the base 30 of theheatsink 10 and into an aligned opening in the circuit board 12. Thefasteners 19 are positioned generally adjacent to the ASIC 20. Thedamping connectors 18 are positioned along an edge of the overhangportion 35 of the heatsink 10 and extend through the base 30 of theheatsink 10 and into the circuit board 12. The overhang portion 35 ofthe heatsink 10 extends beyond an edge of the underlying ASIC parallelto the circuit board, creating an empty space between the overhang andthe circuit board. As previously noted, the base 30 of the heatsink 10may include a two-phase component (e.g., vapor chamber, heat pipes),generally indicated at 58 (details not shown).

It is to be understood that the number of damping connectors 18 andmounting locations shown in FIGS. 1-5 is only an example and that theheatsink mounting system may comprise any number of damping connectors(e.g., 1, 2, 3, 4. . .) positioned in any arrangement, without departingfrom the scope of the embodiments. For example, while only two dampingconnectors 18 are shown located along an edge of the overhang portion 35of the heatsink 10 at opposite corners, additional damping connectorsmay also be inserted in the opening spaced from the edge in the overhangportion of the heatsink (shown in FIG. 3).

The O-rings 37, 38 are installed in an uncompressed state to providezero static force (load) on the heatsink 10. In the uncompressed (free,relaxed) state, the O-rings 37, 38 subject no force on the heatsink 10.When the heatsink begins to flex due to G force from shock or vibration,as indicated at arrow 60 in FIG. 6, the O-ring 37 reacts with a counterforce, indicated at arrow 62 to prevent flexing of the heatsink alongthe length of the heatsink and maintain the heatsink base 30 in agenerally straight (planar) position along the length of the base. Thelower O-ring 38 similarly reacts against the heatsink base 30 uponcontact to absorb energy created due to dynamic loading from shock orvibration at the heatsink. The small cross-section of the O-rings 37, 38provide a reaction force with a small amount of compression. Since theO-rings 37, 38 are installed with no initial compression or deformationthere is zero net force at installation (zero static loading on theheatsink due to the damping connector).

As can be observed from the foregoing, the heatsink mounting systemdescribed herein provides many advantages. For example, in one or moreembodiments, the damping connector 18 provides damping to reduce theamplitude of vibration or shock quickly and effectively, therebyresolving cantilever issues with asymmetric heatsinks. One or moreembodiments also maintain spring forces from fasteners closer to theASIC (or other electronic device) to ensure optimum contact. One or moreembodiments allow for optimum heatsink thermal performance by allowingfor proper mechanical support for two-phase heatsink components such asvapor chamber and heat pipes. One or more embodiments provide minimalimpact on board layout since only two regular sized mounting holes areneeded on the circuit board, also providing minimal cost andmanufacturing impact.

Although the method and apparatus have been described in accordance withthe embodiments shown, one of ordinary skill in the art will readilyrecognize that there could be variations made to the embodiments withoutdeparting from the scope of the invention. Accordingly, it is intendedthat all matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. A heatsink mounting system comprising: aplurality of fasteners for attaching the heatsink to a circuit board ata location proximate to an electronic component interposed between thecircuit board and the heatsink; and a damping connector for attaching anoverhang portion of the heatsink to the circuit board, the dampingconnector comprising: a first O-ring for positioning adjacent to anupper surface of a base of the heatsink; a second O-ring independentfrom said first O-ring for positioning adjacent to a lower surface ofthe base of the heatsink; and a connecting member for extending throughaligned openings in said first O-ring, said second O-ring, and the baseof the heatsink; wherein the damping connector is operable to absorbenergy during vibration or shock at the heatsink to prevent flexing ofthe heatsink along a length of the heatsink, and wherein each of saidfirst and second O-rings is unrestrained around an outer circumferenceof said first or second O-ring and installed in an uncompressed state toprovide zero static load on the heatsink.
 2. The heatsink mountingsystem of claim 1 wherein the connecting member comprises two matingconnectors each comprising a shoulder for supporting said first O-ringor said second O-ring.
 3. The heatsink mounting system of claim 1wherein the fasteners comprise four spring loaded screws.
 4. Theheatsink mounting system of claim 1 wherein the damping connectorcomprises two damping connectors positioned along an edge of saidoverhang portion of the heatsink.
 5. The heatsink mounting system ofclaim 1 wherein the heatsink base comprises a two-phase device to removeheat generated by the electronic component.
 6. The heatsink mountingsystem of claim 5 wherein the two-phase device comprises a vaporchamber.
 7. The heatsink mounting system of claim 1 wherein the heatsinkcomprises a plurality of fins extending from the base and the dampingconnector comprises two damping connectors positioned at corners of saidoverhang portion of the heatsink and aligned with a cutout portion ofthe fins at each of said corners.
 8. The heatsink mounting system ofclaim 1 wherein the heatsink has an aspect ratio of a width to length ofat least one to three.
 9. An apparatus comprising: a heatsink; aplurality of fasteners for attaching the heatsink to a circuit board ata location proximate to an electronic component interposed between thecircuit board and the heatsink; and a damping connector for attaching anoverhang portion of the heatsink to the circuit board, the dampingconnector comprising: a first O-ring adjacent to an upper surface of abase of the heatsink; a second O-ring independent from said first O-ringand adjacent to a lower surface of the base of the heatsink; and aconnecting member extending through aligned openings in said firstO-ring, said second O-ring, and the base of the heatsink; wherein thedamping connector is operable to absorb energy during vibration or shockat the heatsink to prevent flexing of the heatsink along a length of theheatsink, and wherein each of said first and second O-rings isunrestrained around an outer circumference of said first or secondO-ring and installed in an uncompressed state to provide zero staticload on the heatsink.
 10. The apparatus of claim 9 wherein theconnecting member comprises two mating connectors each comprising ashoulder for supporting said first O-ring or said second O-ring.
 11. Theapparatus of claim 9 wherein the damping connector comprises two dampingconnectors positioned along an edge of said overhang portion of theheatsink.
 12. The apparatus of claim 9 wherein the heatsink basecomprises a two-phase device to remove heat generated by the electroniccomponent.
 13. An apparatus comprising: a circuit board; a heatsinkmounted on the circuit board; a plurality of fasteners attaching theheatsink to the circuit board at a location proximate to an electroniccomponent interposed between the circuit board and the heatsink; and adamping connector attaching an overhang portion of the heatsink to thecircuit board, the damping connector comprising: a first O-ring adjacentto an upper surface of a base of the heatsink; a second O-ringindependent from said first O-ring and adjacent to a lower surface ofthe base of the heatsink; and a connecting member extending throughaligned openings in said first O-ring, said second O-ring, and the baseof the heatsink and attached to the circuit board; wherein the dampingconnector is operable to absorb energy during vibration or shock at theheatsink to prevent flexing of the heatsink along a length of theheatsink, and wherein each of said first and second O-rings isunrestrained around an outer circumference of said first or secondO-ring and installed in an uncompressed state to provide zero staticload on the heatsink.
 14. The apparatus of claim 13 wherein the dampingconnector comprises two damping connectors positioned at corners of saidoverhang portion of the heatsink.
 15. The apparatus of claim 13 whereinthe heatsink base comprises a two-phase device to remove heat generatedby the electronic component.
 16. The apparatus of claim 13 wherein thefasteners comprise four spring loaded screws and the damping connectorcomprises two damping connectors.
 17. The apparatus of claim 13 whereineach of said first and second O-rings is positioned between a flatsurface of the heatsink base and a flange defined by a screw head.